The goal of this research at BioMetallics is to develop a rapid, easy to use enzymeimmunoassay, with enhanced sensitivity for determining the reproductve hormone, progesterone, in saliva. The measurement of progesterone in saliva is attractive because sampling is noninvasive and essentially stress free. But because progesterone levels in saliva are only 1% of progesterone levels in serum, enhanced sensitivity is required over conventional enzymeimmunoassay methodology. A method for increasing the enzyme sensitivity of horseradish peroxidase is presented. This method will be demonstrated by the development of an assay kit for progesterone in saliva. This enhanced sensitivity method will also have general application to the determination of low levels of many other hormones or analytes of interest.